Apparatus and methods for activating a downhole tool

ABSTRACT

An apparatus for performing a downhole operation in a wellbore comprises a tool string deployed on a slickline into the wellbore, where the tool string comprises a controller and a tool. A motion detector is disposed in the controller and senses motion of the tool string and generates a first signal in response thereto. A device disposed in the controller detects a downhole parameter of interest and generates a second signal in response thereto. A processor in the controller acts according to programmed instructions to activate the tool when the first signal is below a first preset threshold for at least a preset time interval, and the second signal exceeds a second preset threshold. A method of using the apparatus is also provided.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention pertains to oil field operations and moreparticularly to an apparatus and methods for activating a downhole tool.

2. Related Prior Art

A number of operations may be performed in a common oil wellbore byrunning tools in on a line that is controlled from the surface. In manycases, hardware for logging, perforating, and flow control may be runinto the hole on slickline. Slickline commonly comprises a thin,nonelectric cable used for selective placement and retrieval of wellborehardware. Downhole valves and sleeves can also be adjusted usingslickline tools. In many such tools, such as battery powered loggingtools, it is desirable to control the turn-on and operation of the toolsfrom the surface. Such tools may contain, for example, caliper arms thatcontact the borehole wall enable logging tool sensor contact with theformation surrounding the wellbore. These arms must be in a collapsedstate during transit to prevent the tool from hanging up on the way intothe wellbore. In other instances, such as with perforating guns, it isdesirable to prevent their arming and possible firing until they aresafely downhole.

Without electrical communication to the surface, prior art tools haveused several techniques for actuating such tools downhole. These includeraising the bottomhole pressure by a predetermined amount such that apressure sensor in the downhole tool senses the increased pressure as asignal to actuate. The pressure increase may be in the form of a staticincrease or in the form of a sequence of pressure pulses that aredetected downhole. However, the bottomhole pressure in a well iscommonly balanced to hold back formation fluid ingress to the wellborewhile not exceeding the fracture pressure of the formation surroundingthe wellbore. The increased pressure signal, in many instances, may besufficient to cause fractures in the formation. Even if the formationdoes not fracture, the increase pressure in the wellbore may besufficient to force wellbore fluids to invade the formation and causeerrors in subsequent logging operations.

In another prior art downhole tool, a preset time interval is set in atimer in the tool at the surface such that the tool is then deployed tothe desired location before the preset time interval has been exceeded.When the preset time interval is exceeded, the tool is activated.Problems in deploying the tool may occur that causes the preset timeinterval to be exceeded before the tool is properly deployed. Activationof the tool may cause the tool to be stuck in the hole, or cause damageto the wellbore.

There is a demonstrated need for a reliable, safe method of activatingslickline tools downhole. The present invention addresses these andother shortcomings of the prior art described above.

SUMMARY OF THE INVENTION

In one aspect of the present invention, an apparatus for performing adownhole operation in a wellbore comprises a tool string deployed on aslickline into the wellbore, where the tool string comprises acontroller and a tool. A motion detector is disposed in the controllerand senses motion of the tool string and generates a first signal inresponse thereto. A device disposed in the controller detects a downholeparameter of interest and generates a second signal in response thereto.A processor in the controller acts according to programmed instructionsto activate the tool when the first signal is below a first presetthreshold for at least a preset time interval, and the second signalexceeds a second preset threshold.

In another aspect, a method of activating a downhole tool in a wellborecomprises deploying a tool string on a slickline into the wellbore. Thetool string is held substantially motionless for at least a preset timeinterval at a location in the wellbore. A motion detector determinesthat the tool string is substantially motionless for at least the presettime interval. It is determined that a downhole detected parameter ofinterest exceeds a second preset threshold. A tool is activated in thetool string when both the tool is substantially motionless for at leasta preset time interval, and a downhole detected parameter of interestexceeds a second preset threshold.

These and other aspects of the present invention are more clearlydescribed in the drawings and specification that follows.

BRIEF DESCRIPTION OF THE DRAWINGS

For detailed understanding of the present invention, references shouldbe made to the following detailed description of the preferredembodiment, taken in conjunction with the accompanying drawings, inwhich like elements have been given like numerals and wherein:

FIG. 1 is a sketch of an exemplary tool string deployed on a slickline;

FIG. 2. is a block diagram of the tool string; and

FIG. 3 is a block diagram depicting an example of the operation of oneembodiment of the present invention.

DESCRIPTION

Referring initially to FIG. 1, there is shown an exemplary downhole toolstring 11 comprising downhole controller 10 and tool 18. Tool string 11is supported by slickline 12. Slickline 12 extends from rig 14 at thesurface 16. Slickline 12 is deployed from winch 29 around one or moresheave wheels 26, supported from rig 14, and down borehole 20. Surfacecontroller 28 provides suitable power and controls associated with winch29 for controlling the deployment of the slickline into borehole 20.Alternatively, winch 29 may be separately controlled and surfacecontroller 28 may be a portable computer, such as a personal computer,having appropriate interfaces circuitry to communicate, at the surface,with downhole controller 10. Tool string 11 is deployed adjacentproduction zone 22 located, for example, near the bottom 24 of borehole20, also called a wellbore. Borehole 20 commonly has a fluid 13 disposedtherein which may be a drilling fluid (also called drilling mud), aproduction control fluid, and/or a produced fluid from production zone22. The produced fluid may be water, hydrocarbon liquid, gas, or anycombination of the above.

Tool 18 may include multiple downhole tools including but not limitedto: a logging tool, a perforating gun, a packer, a flow control valve,and/or any other device suitable for running on slickline 12 andperforming downhole operations. The logging tool includes, but is notlimited to: an acoustic tool, a density tool, a neutron tool, aninduction resistivity tool, an NMR tool, and a gamma ray tool. Thelogging tool may be a single tool or any combination of such tools, asdescribed above. The downhole tools may be exposed to fluid pressures upto 30,000 psi and temperatures up to 500° F. The downhole fluid may bebrine, water based drilling fluid, oil base drilling fluid and/or fluidsthat may contain hydrogen sulfide, carbon dioxide, methane, and otherdeleterious compounds.

FIG. 2 is a block diagram of an exemplary embodiment of downholecontroller 10 of the present invention. Downhole controller 10 includesprocessor 31 having sufficient memory therein for storing programmedinstructions for operating downhole controller 10 and for storing presetsensor thresholds for use in the present invention. Circuits 32interface processor 31 with clock 35, motion sensor 33, pressure sensor34, and temperature sensor 39 and with tool 18. Clock 35 is a crystaloscillator and is used to measure elapsed time from a start signalinitiated by surface controller 37 before tool string 11 is deployed inwellbore 20. Clock 35 may be adapted to provide real-time. Motion sensor33, pressure sensor 34, and temperature sensor 39 are also disposed incontroller 10. Motion sensor 33 is used to determine when tool string 11is motionless. Clock 35 also contains a timer for determining the lengthof time that the tool is held substantially motionless. In oneembodiment, accelerometers 60 are mounted in controller 10 and used todetect motion of tool string 11. Lack of motion is determined when asignal from the accelerometers is below a preset threshold level. Itshould be noted that the threshold level is somewhat applicationdependent and is field settable. For example, in a well with fluidflowing past the tool, there will be flow turbulence affecting theaccelerometer signal level even when slickline 12 is being held steadyat the surface. In a non-flowing well, the accelerometer threshold maybe set at a lower level. Alternatively, motion may be detected by anoise sensor 61 that detects the noise associated with the contact oftool string 11 with the wall of wellbore 20 and the flow noiseassociated with the movement of tool string 11 through either a staticor flowing fluid in wellbore 20. Noise sensor 61 may include apiezoelectric crystal and/or a piezoelectric film mounted on controller10 such that noise sensor 61 is exposed to fluid 13 in wellbore 20.Power source 36 provides power to operate controller 10 and itsassociated devices. In one embodiment, power source 36 includesbatteries (not separately shown) suitable for downhole use. Suchbatteries are commercially available and are not described here further.Controller 10 is electrically and mechanically coupled to tool 18 usingtechniques known in the art. Power source 36 contains sufficient powerto operate tool 18. Alternatively, tool 18 contains its own separatepower source.

Pressure sensor 34 and temperature sensor 39 are mounted in controller10 such that they are able to measure the steady-state downhole pressureand temperature of fluid 13 in wellbore 20. Such sensors arecommercially available and will not be described here.

Processor 31 contains programmed instructions for determining when toactivate tool 18. FIG. 3 shows an operational flow chart of an exemplaryoperation of the present invention. Depending on the particular desireddownhole location of interest and the nature of the downhole operation,in step 40, a motion sensor threshold and a length of time that the toolmust be motionless are programmed into processor 31 at the surface andprior to deployment into wellbore 20, using a connection to surfaceprocessor 28. At least one additional parameter threshold is alsodownloaded by the operator into processor 31, prior to deployment, usinga connection to surface processor 28.

Tool string 11 is deployed into wellbore 20 in step 45. Motion detectionis continuous during the entire downhole operation. The tool is stoppedand held substantially motionless in step 46. In step 47, the motiondetection sensor signal falls below the preset threshold level, andclock 35 begins a separate timer to determine the length of time thatthe tool is motionless and compare the measured time interval to thepreset motionless threshold interval. When the motionless time periodexceeds the preset motionless threshold interval, controller 10 proceedsto sense the additional parameter of interest and compare themeasurement to its preset threshold value in step 48. The additionalparameter may be downhole pressure, downhole temperature, and/or a totaldeployment time interval. At least one additional parameter is used.However any number or combination of the additional parameters may beused. If all of the criteria are met, then downhole tool 18 is activatedin step 49.

In one example, the tool may be programmed to activate when all of thefollowing conditions are met:

-   -   the motion detector signal remains below the motion threshold        for 5 minutes; and    -   the bottomhole pressure is at least 5000 psi; and    -   the bottomhole temperature is at least 80C; and    -   the tool deployment time is at least 90 minutes.        As seen in this example, the tool may be safely handled at the        surface, and activation downhole does not require an increase in        bottomhole pressure.

While described above as separate devices, in another embodiment,controller 10 may be included as part of tool 18.

While there has been illustrated and described a particular embodimentof the present invention, it will be appreciated that numerous changesand modifications will occur to those skilled in the art, and it isintended in the appended claims to cover all those changes andmodifications, wherein the word “comprising”, as used throughout theclaims, is to be interpreted to mean “including but not limited to.”

1. An apparatus for performing a downhole operation in a wellbore,comprising: a. a tool string deployed on a slickline into the wellbore,the tool string comprising a controller and a tool; b. a motion detectordisposed in the controller sensing motion of the tool string andgenerating a first signal in response thereto; c. a device disposed inthe controller detecting a downhole parameter of interest and generatinga second signal in response thereto; d. a processor in the controlleracting according to programmed instructions to activate the tool whenthe first signal is below a first preset threshold for at least a presettime interval and the second signal exceeds a second preset threshold.2. The apparatus of claim 1, wherein the motion detector is chosen fromthe group consisting of: an accelerometer and a noise sensor.
 3. Theapparatus of claim 1, wherein the device is chosen from the groupconsisting of: a pressure sensor, a temperature sensor, and a downholeclock.
 4. The apparatus of claim 1, wherein the second preset thresholdis chosen from the group consisting of: a fluid pressure, a fluidtemperature, and a deployed time interval.
 5. The apparatus of claim 1,wherein the controller comprises: a. the processor having a memorycapable of storing programmed instructions; and b. a downhole clock. 6.The apparatus of claim 1, wherein the tool is chosen from the groupconsisting of: a logging tool, a perforating gun, a packer, and a flowcontrol valve.
 7. The apparatus of claim 1, wherein the tool comprises aplurality of tools.
 8. A method of activating a downhole tool in awellbore, comprising: a. deploying a tool string on a slickline into thewellbore; b. holding the tool string substantially motionless for atleast a preset time interval; c. detecting that the tool string issubstantially motionless for at least the preset time interval; d.determining that a downhole detected parameter of interest exceeds asecond preset threshold; and e. activating a tool in the tool stringwhen both step c. and d. are met.
 9. The method of claim 8, wherein, thetool string comprises a controller and a tool.
 10. The method of claim8, wherein the step of detecting that the tool string is substantiallymotionless comprises determining that a signal from a motion detector isbelow a first preset threshold at least the preset time interval. 11.The method of claim 10, wherein the motion detector is chosen from thegroup consisting of: an accelerometer and a noise sensor.
 12. The methodof claim 8, wherein the downhole detected parameter of interest ischosen from the group consisting of: a downhole fluid pressure, adownhole fluid temperature, and a deployed time interval.
 13. The methodof claim 8, wherein the tool is chosen from the group consisting of: alogging tool, a perforating gun, a packer, and a flow control valve. 14.The method of claim 8, wherein the tool comprises a plurality of tools.